pundit: convert tag aliases / implications to pundit.

app/policies/tag_alias_policy.rb

@@ -0,0 +1,5 @@
+class TagAliasPolicy < ApplicationPolicy
+  def destroy?
+    user.is_admin?
+  end
+end

app/policies/tag_implication_policy.rb

@@ -0,0 +1,5 @@
+class TagImplicationPolicy < ApplicationPolicy
+  def destroy?
+    user.is_admin?
+  end
+end